A Catholic bishop will have to abdicate as co-prince of Andorra if the country tries to legalise abortion, the Vatican has reportedly said.

France Bleu reports that Pope Francis himself telephoned Andorran Prime Minister Toni Martí to tell him that if the principality were to legalise abortion, the Bishop of Urgell could no longer serve as the country’s head of state – however local media simply says “the Vatican” contacted Martí.

Under a centuries-old arrangement, the Bishop of Urgell and the French President serve as co-princes of the country, which is located in the Pyrenean mountains on the border between France and Spain.

Although a new constitution in 1993 created a parliamentary democracy, laws still have to receive assent from the two co-princes. Archbishop Joan Enric Vives i Sicília, who holds the rank of archbishop as a personal title, has been bishop since 2003.

Currently, women who want abortions can travel across the border to the country’s two larger neighbours, where the practice is legal. However, feminist activists have become increasingly vocal in demanding that the small country also legalise the procedure.

Abortion lobbyists have claimed that only the French Co-Prince need sign any pro-abortion legislation, and that the Episcopal Co-Prince, as the bishop is known, may be excused – as happened when the country legalised divorce in the 1990s.

However, the Vatican has made it clear that any attempt to force through a pro-abortion law would be incompatible with the Bishop of Urgell remaining head of state, throwing the country into a constitutional crisis.

The country dates its independence back to 1268, when the Bishop of Urgell and the Count of Foix resolved a dispute over the territory by agreeing to share sovereignty. Eventually, the counts of Foix succeeded as kings of France. The bishops of Urgell and French heads of state have jointly ruled the country ever since.

The shared sovereignty has meant that the tiny principality, a remnant of feudal Europe, has remained independent while others have vanished.

Andorran Interior Minister Xavier Espot said the Church’s position is “well known”, and that the country’s head of state is “unique and indivisible”, implying that if the bishop goes, the French President will have to go too. The entire Andorran state would be at risk, Espot said.

The Diocese of Urgell has remained largely quiet on the issue, except to say Archbishop Vives is “not worried”.